The present invention relates to guide wheel equipment of the type used for allowing road vehicles to travel along rails of a railroad track. It further relates to a vehicle having such rail guide wheel equipment mounted thereon.
As used herein, a road vehicle is a vehicle having wheels which contact a highway or other road, as opposed to only having wheels which roll on rails on a railroad track.
Railroad service crews often have to go to various places along a railroad track in order to make repairs and inspections. Depending upon the type of service which is performed and other factors, the service crew may ride to the work site using a rail vehicle or using a road vehicle, such as a truck or car. Since the best way to a work site may include travel along a road and travel along a railway, service crews and other rail workers often have used road vehicle having a rail engagement or guide wheel apparatus mounted on them. Such cars or trucks may travel along a highway or other road with road wheels engaging the road. Upon getting to an appropriate place along the railway, the rail engagement apparatus is operated such that railway wheels are lowered from the vehicle until the vehicle is bound to the railway. Such vehicles include an apparatus at the front of the vehicle which lifts the front road wheels off the ground or at least takes some loading off the front road wheels when two front railway wheels engage rails and an apparatus at the back of the vehicle, which apparatus secures the back of the vehicle to the rails by two back railway wheels. The two back railway wheels allow the regular road wheels to contact the rails or other surface such that the road wheels may provide traction to move the vehicle even when the two front railway wheels and two back railway wheels have secured the vehicle to the rail. When the vehicle wishes to leave the railway, the two front railway wheels and the two back railway wheels are retracted or lifted up such that the vehicle may again run along the road. In those units where the front road wheels contact a lower surface even in the rail mode, the front road wheels may help in braking the vehicle.
Various structures have been used to allow railway wheels to be attached to road vehicles. Although such structures have been generally useful at moving the railway wheels between an upper position in which the vehicle may travel along a highway or other road and a lower position in which the vehicle travels along a railway, such structures have often been subject to one or more of several disadvantages.
Such structures move the rail guide wheels between an upper road position corresponding to a highway or road mode and a lower rail position corresponding to a rail mode. In the road mode, the rail guide wheels are in their upper road position such that road wheels move and control the vehicle movement along a highway or other road surface. In the rail mode, the rail guide wheels are in their lower rail position such that the vehicle is engaged to the rails of a railroad track for movement thereon. The rear road wheels of the vehicle still provide the propulsion, although the weight on those wheels is somewhat reduced by the lowering of a back pair of rail wheels.
Such prior designs of guide wheel structures require that the guide wheel structure be stable when the guide wheels are in their road and in their rail positions. Mechanisms are used for raising and lowering the rail guide wheels. In order to stabilize the rail engagement wheels in both rail and road positions, various techniques have been used.
Commonly, locking pins or similar devices are manually placed or manipulated to lock the mounting structures of the wheels in the road and/or the rail positions. These generally work well, but they require extra time for the vehicle driver or other worker to perform the manual manipulation.
Other locks have been used which provide automatic locking in at least one of the positions (road or rail), but such mechanisms often add to the cost and complexity of the design. Depending upon how complex they are and the specifics of their design, malfunction or improper operation may be a problem.
At least one prior design has used an overcenter linkage which is stabilized in one position by use of a link which goes to an overcenter position such that it and the attached guide wheel supports will be quite stable in that position. However, the opposite position (road or rail) will still require other locking or stabilizing techniques.
A further disadvantage of prior guide wheel structures is that they usually require a relatively high torque in order to move between rail and road positions. Since hydraulic cylinders are used to provide the high torque requirements, this in turn requires that a hydraulic system be added to the road vehicle on which the guide wheel structures are added. Adding the hydraulic components increases the weight, cost, and complexity of the road/rail vehicle which is usually constructed by modifying a road vehicle.